There are a number of systems that use existing radio receivers in automobiles to playback audio signals from a compact disc (CD) player, tape cassette player, satellite broadcast receiver, or other auxiliary audio sources.
In these systems, it is required to set the reception frequency of the installed radio receiver to a specific frequency of the frequency modulation (FM) broadcasting band where no FM programs are broadcasted, namely an empty frequency or an unused frequency. Next, the transmission frequency of the electronic entertainment device must be tuned to the reception frequency of the radio receiver. However, such tuning operations require very cumbersome manipulations. In particular, very cumbersome and heavy workloads are necessary so as to scan for the empty frequency in such a frequency band where a large number of FM programs are broadcasted.
To solve such problem, special systems are capable of automatically selecting an empty or unused frequency within an FM broadcasting band, and to transmit the FM signals at this empty frequency. For example, one kind of special systems automatically detects an unused frequency within the FM broadcasting band and sets a transmission frequency and a reception frequency to the detected empty or unused frequency, and also further displays the transmission frequency.
However, because the empty or unused frequency varies at different location, I.e., when an automobile implemented with the wireless transmission system moves from a municipal area to another municipal area, the empty or unused frequency may be interfered by a local broadcasting station, which results in poor transmitted FM signals.
Thus, an improved wireless transmission system and method which automatically selects the transmission frequency when the FM signals is interfered is needed in order to ensure a non-interfered transmitted FM signals.